The polymer layers of a protective glove constitute barrier layers. The protective effect, i.e. the ability of the protective glove to protect against a chemical depends on the permeability, i.e. on the permeation process. This process includes the steps of adsorption, diffusion, and desorption. While adsorption processes between the chemical and the polymer affect the degree of swelling and dissolving or solubilization of the polymer surface, the diffusion rate determines how quickly the respective chemical permeates the polymer layer. The total velocity of all of the permeation steps is defined as the permeation rate. The permeation time, also referred to as breakthrough-time, is the amount of time from the contact of the chemical with the polymer surface until it permeates through the barrier layer; it serves as a measure for the protective effect of the respective layer. Accordingly, polymers that have a long permeation time for a certain chemical offer a good protection against the relevant compound over a comparatively long period of time. On the one hand, the permeation time depends on the structure of the polymer; nonpolar polymers tend to have long permeation times for polar solvents and polar polymers tend to have long permeation times for nonpolar solvents. Due to the availability of a multitude of suitable polymers, in particular elastomers, protective gloves are available for a large number of chemical substance classes. In the context of the present disclosure, an elastomer is understood to be a cross-linked, flexible polymer. Corresponding polymers without cross-linking or with only a low degree of cross-linking are referred to as rubbers (see standard DIN 53501). A protective glove composed of only one polymer is only resistant to a narrow range of chemicals. It is desirable, however, for a protective glove to have long permeation times for the largest possible number of chemical substance classes and thus to offer the user a broad range of protection. In practice, this is achieved through the use of composite materials composed of a plurality of polymers with different physical and chemical properties. Thus protective gloves composed of cross-linked butyl rubber and fluororubber have a favorable resistance to both nonpolar solvents such as aliphatic hydrocarbons and polar solvents such as alcohols. A polymer composite material of this kind, however, does not cover all chemical substance classes. It is not possible, for example, to provide satisfactory protection from chlorinated hydrocarbons and ethers such as tetrahydrofuran. By contrast with the above-described polymer composite materials, mixed layers such as polymer blends do not offer any comparable synergistic effects with regard to their protective effect.
Polar polymers such as polyvinyl alcohol (PVA) offer good levels of resistance to nonpolar chemicals such as chlorinated hydrocarbons, aromatics, and ethers. In particular, PVA is one of the few polymers that do not swell or dissolve when exposed to polychlorinated hydrocarbons such as chloroform or aliphatic ethers such as tetrachloroethane and therefore have long permeation times for these compounds. However, PVA has a low resistance to polar chemicals such as low-molecular alcohols, esters, or ketones. The greatest challenge in dealing with PVA lies in its water solubility and its sensitivity to hydrolysis. This can be reduced on the one hand through cross-linking. PVA can also be stabilized by a high degree of hydrolysis grade, i.e. by means of the share of hydroxyl groups in the polymer. Consequently, a high degree of hydrolysis grade results in larger crystalline domains within the polymer, which are more difficult to dissolve than amorphous regions. However, the degree of hydrolysis grade and the degree of cross-linking reduce the elasticity of PVA, which is disadvantageous when it is used in protective gloves. An extensive stabilization of PVA without reducing the flexibility is thus at the very least difficult if not impossible.
The published, unexamined patent application DE 2,330,316 discloses a protective glove that is made of a composite material composed of PVA and a rubber and, by means of the PVA layer, also provides protection against aromatics and chlorinated hydrocarbons. The PVA forms a film on the rubber; the inside of the glove is formed by the rubber layer and is intended to protect the user of the protective glove from moisture. The problem with this design is that the PVA hydrolyzes over time. Patent disclosure document DE 2,759,008 A1 describes a protective glove that is composed of a woven textile—which, by means of a dip-coating process, has been coated with polymers such as polyvinyl chloride (PVC) or polyvinyl alcohol (PVA)—as well as a method for its manufacture and the apparatus designed for this purpose. Such a glove, however, is only resistant to a narrow range of chemical substance classes.
The document WO 02/080,713 A2 describes a protective glove composed of a polymer composite material that contains PVA. The PVA is in the form of a gel and is embedded between two elastomer layers. The layers are applied through coagulation, i.e. through precipitation of particles from dispersions with the aid of flocculants. The layer over the PVA functions as a moisture barrier and is composed of a synthetic rubber such as carboxylated nitrile rubber. No details about the protective effect are specified.
The patent application US 2009/0,068,443 A1 discloses a protective glove composed of a polymer composite material containing PVA. The PVA layer is protected from moisture by a subsequent rubber layer, but layers of adhesive are used. In order to increase the mechanical and chemical resistance, a resin based on a dispersion of polytetrafluoroethylene (PTFE) and SiO2 is also provided as a top layer. A resin of this kind is disadvantageously inflexible. In addition, the protective glove is produced by means of a dip coating process, where it is dipped into dispersion, which is disadvantageous insofar as the precipitation of the polymer requires the use of precipitants.